Recycled Poly Research Articles

Enhanced Impact Strength of Recycled PET/Glass Fiber Composites.

In this paper, we report a study on the effects of different ethylene copolymers in improving the impact strength of a fiber-reinforced composite based on a recycled poly(ethylene terephthalate) (rPET) from post-consumer bottles. Different ethylene copolymers have been selected in order to evaluate the effects of the polar co-monomer chemical structure and content. The composite mixtures were prepared via melt extrusion, and the samples were manufactured by injection molding. Impact strength was evaluated using Izod tests, and a morphological study (FESEM) was performed. As a result, a composite with substantially improved impact properties was designed. This study demonstrates that a post-consumer PET from the municipal waste collection of plastic bottles can be successfully used as a matrix of high-performance, injection-molded composites, suitable for use in the automotive sector, among others, with no compromise in terms of mechanical requirements or thermal stability.

Mechanical and viscoelastic properties of polyethylene‐based microfibrillated composites from 100% recycled resources

AbstractIn this study, recycled polyethylene (rPE) based microfibrillated composites (MFCs) were developed while incorporating recycled poly(ethylene terephthalate) (rPET) and recycled polyamide 6 (rPA) as the reinforcing fibrillar phases at a given weight ratio of 80 wt% (rPE)/20 wt% (rPET or rPA). The blends were first melt processed using a twin‐screw extruder. The extrudates were then cold stretched at a drawing ratio of 2.5 to form rPET and rPA fibrillar structures. Next, the pelletized drawn samples were injection molded at the barrel temperatures below the melting temperatures of rPET and rPA. The tensile, three‐point bending, impact strength, dynamic thermomechanical, and rheological properties of the fabricated MFCs were analyzed. The effects of injection molding barrel temperature (i.e., 150°C and 190°C) and extrusion melt processing temperature (i.e., 250°C and 275°C) on the generated fibrillar structure and the resultant properties were explored. A strong correlation between the fibrillar morphology and the mechanical properties with the extrusion and injection molding temperatures was observed. Moreover, the ethylene/n‐butyl acrylate/glycidyl methacrylate (EnBAGMA) terpolymer and maleic anhydride grafted PE (MAH‐g‐PE) were, respectively, melt processed with rPE/rPET and rPE/rPA6 blends as compatibilizers. The compatibilizers refined the fibrillar structure and remarkably influenced mechanical properties, specifically the impact strength.

Recycled PET foaming: Supercritical carbon dioxide assisted extrusion with real-time quality monitoring

Foaming of recycled poly(ethylene terephthalate) (rPET) was performed by supercritical carbon dioxide (sc-CO 2 ) assisted extrusion. The intrinsic viscosity (IV) of rPET was increased from 0.62 dl/g to 0.87 dl/g using an epoxy-functional chain extender, which provided adequate rheological properties for cell stabilization so that an apparent density of less than 0.15 g/cm 3 became achievable. Homogeneous and talc induced heterogeneous crystal and cell nucleation, subsequent cell growth and stabilization processes were examined using differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. It was found that using talc the crystallization temperature increases which results in smaller cell size distribution. A strong correlation was evinced between the apparent density and the Fourier transform near-infrared (NIR) spectrum of the foamed rPET samples enabling quick and non-destructive characterization. Accordingly, NIR spectroscopy is demonstrated as a suitable method for in-line quality monitoring during extrusion foaming of recycled PET, being especially prone to quality fluctuations.

Creep Behaviour of Recycled Poly(ethylene) Terephthalate Non-Woven Geotextiles.

At the beginning of this century, due to well-established Brazilian recycling processes, geosynthetics’ manufacturers started to use recycled poly(ethylene) terephthalate (PET) yarns/filaments (from PET bottles) in geotextile production. Despite the fact that recycled products cannot act as reinforcement functions, geosynthetics are constantly under sustained tensile load and experiences evolutions of the axial strain (creep behaviour). Thus, this study aims to assess the influence of the structure of (needle-punched) non-woven geotextiles manufactured using recycled PET yarns on their creep behaviour. Two geotextiles with different fibre/filament production processes were investigated (short-staple fibres—GTXnwS—and continuous filaments—GTXnwC). Unconfined in-isolated conventional and accelerated (using the stepped isothermal method) creep tests were performed at 5%, 10%, 20%, 40% and 60% of geotextiles’ ultimate tensile strength. The geotextiles investigated provided similar creep behaviour to geotextiles manufactured with virgin PET material. The standard deviation of the axial strain tends to increase as the load level applied increase. The structure of the GTXnwS harms its tensile –strain behaviour, promoting axial deformation under sustained loads, at least 50% higher than GTXnwC for the same load level applied. The influence of the load level and geotextile structure in the initial axial strain is pointed out. Long-term predictions based on creep tests performed using the stepped isothermal method have proven to be conservative and they must be restricted for quality control of the investigated geotextiles.

Viscosity improvement of recycled poly (ethylene terephthalate) from waste bottles by adding antioxidants and chain-extender

This research work is focused on the viscosity improvement of recycled poly(ethylene terephthalate) (rPET) from waste bottles by adding antioxidants and multi-functional reactive polymer (Joncry ADR 4468, chain extender). The achieve the objective of this work the investigated was broken into two parts. The first part studied the effect of rPET viscosity after adding various types of antioxidants and stabilizer such as Irgafos®168, Tinuvin® 770, Irganox®1010. The second part observed the effect of viscosity after it was blended with chain extender at 0, 0.2, 0.4, 0.6 and 0.8 pph. rPET was then dried in the oven at 120 oC for 12 hrs, to deplete the moisture. Then, the dried rPET (mixed with the chemicals above) was extruded into a compound using a twin screw extruder. The shear viscosity of the extruded compound was then measured using a rotational rheometer at 270 oC. The results revealed that the addition of chain extender increased the shear viscosity and the tensile strength at break of rPET. Therefore, the chain extender interacted with chains, which could change the structure to be the longer chains, branching or network structures. These structures are entangled and interrupt the movement of the molecular chains. It can be concluded that the viscosity of rPET can be improved by adding a chain extender at 0.6 pph, and the antioxidants of Irgafos®168, Tinuvin®770 and Irganox®1010 at 0.2, 0.1 and 0.5 pph, respectively.

Effect of silane treated fly ash on physico‐mechanical, morphological, and thermal properties of recycled poly(vinyl chloride) composites

AbstractThe silane treatment on properties of fly ash (FA) and development of its composite using recycled poly(vinyl chloride) (r‐PVC) material retrieve from waste wires and cable insulation are investigated in this work. The use of (3‐aminopropyl)triethoxysilane was employed as a coupling agent with some other essential additives. The composites sheet was prepared by means of the melt mixing process and go along with the compression molding process. The superior properties on compatibility between silane‐modified FA (FA(Si)) and r‐PVC were successfully studied using rheological, thermomechanical, morphological, and water absorption analysis. Primary analysis of r‐PVC and FA was employed using Fourier transform infrared spectroscopy analysis. The thermal stability of composites was stable up to 187°C. In addition, significant enhancement on tensile strength as well as young's modulus of composite as compared to untreated r‐PVC/FA composites. Morphological properties of silane treated FA based composites presented the good distribution and excellent uniformity with higher wettability of FA particles within r‐PVC matrix. The water absorption test showed decrease in water absorption with increase silane treatment concentration FA in the r‐PVC matrix. It was remarkable to note that silane treated FA can be prepared as a composite using r‐PVC matrix with further modified properties.

Green Composites Based on Unsaturated Polyester Resin from Recycled Poly(Ethylene Terephthalate) with Wood Flour as Filler-Synthesis, Characterization and Aging Effect.

The paper investigates the synthesis of green composites and their properties before and after the laboratory accelerated aging tests. Materials were made of unsaturated polyester resins (UPRs) based on recycled poly(ethylene terephthalate) (PET) and wood flour (WF). The effect of dibenzylideneacetone (dba) addition on mechanical and thermomechanical properties was also determined. Green composites were obtained using environment friendly polymeric cobalt as an accelerator. Before and after exposition to the xenon lamp radiation, the UPRs physically modified by WF were characterized only by a greater flexural modulus compared with the analogous composites based on the pure resin. Addition of dba caused the increase of flexural modulus, flexural strength, strain at break and mechanical loss factor compared to the non-modified material. After aging only the last mentioned parameter took on lower values compared to the pure resin analogues.

Pin hole tensile and fatigue properties of self-reinforced PET composites

This study investigates the effects of the width-to-hole diameter ratio (W/D) and the edge distance-to-hole diameter ratio (E/D) of a specimen on the bearing properties of self-reinforced recycled poly (ethylene terephthalate) (srrPET) composites with (srrPET-FR) and without flame retardant under a tensile and tensile-tensile fatigue load. The bearing strength of srrPET composites is largely dependent on the W/D ratios, whereas E/D ratios did not show any significant influence. The srrPET composites exhibited higher fatigue cycles compared with the srrPET-FR composites at the same (stress amplitude) σa. Higher W/D ratios resulted in a higher fatigue strength for srrPETs. The compact constitutive equation used to predict the curves between σa and number of cycles to failure (Nf), well agree with the experimental results.

Rheological modification of recycled poly(ethylene terephthalate): Blending and reactive extrusion

The use of recycled PET (rPET) in long-term applications, such as composites, may provide an environmentally friendly solution for PET wastes. Main problem to overcome to use rPET in composites is its high viscosity which compromises the impregnation with the fibers during the consolidation process. As it is well known, PET undergoes thermo-mechanical and hydrolytic degradation during its mechanical recycling decreasing its viscosity and causing a loss of mechanical properties. For this reason, this paper takes into consideration a rheological modification during mechanical recycling to achieve the necessary fluidity for composites while maintaining the mechanical properties. Rheological modification was carried out by physical and chemical methods. Physical method was realized through blending with virgin PET (vPET) of low melt viscosity. Chemical method was performed on rPET, vPET and its blends by reactive extrusion. The effect of rheological modifications on the final thermal and mechanical properties was studied. Main results showed that both methods are able to decrease the viscosity without compromising mechanical properties. In addition, the chemical method during the reactive extrusion provided higher Elastic Modulus values.

Reduction of molar mass loss and enhancement of thermal and rheological properties of recycled poly(lactic acid) by using chain extenders obtained from RAFT chemistry

The synthesis of block copolymers of glycidyl methacrylate (G), styrene (S) and acrylonitrile (AN) (represented as GS-SAN) by reversible addition–fragmentation chain transfer (RAFT) polymerization, with well-defined average molar masses and epoxy functionalities, and evaluation of their performance as macromolecular chain extenders for recycled poly(lactic acid) (rPLA), is reported. The introduction of the GS-SAN chain extenders during the extrusion processing of rPLA leads to recovery of molar mass as well improvement of thermal stability and rheological properties, compared to recycled unmodified PLA. Differential scanning calorimetry (DSC) results revealed a reduction in cold crystallization temperature and an increase in the degree of crystallinity of chain extended rPLA. Increasing epoxide content in the synthesized block copolymers leads to increased degrees of crystallinity. The rheological study revealed that the GS-SAN copolymers allowed significant increases in modulus, strength and complex viscosity of chain extended rPLA, indicating that better mechanical performance and processability were obtained. These increases become more pronounced as the concentration of reactive epoxy functional group is increased.

The effect of kenaf loading on the mechanical properties of kenaf-reinforced recycled poly(ethylene terephthalate)/recycled poly(propylene) (rPET/rPP) composite

Kenaf fibre as a natural lignocellulos is fast receiving encouraging attention in bio-composite material because it offers a range of properties that may be difficult to obtain with other synthetic reinforcements. The aim of this study is to compare the mechanical properties of kenaf bast and core fibre reinforced recycled poly(ethylene terephthalate) (rPET)/recycled poly(propylene) (rPP) composite with varying fiber loading i.e. 0, 5, 10, 15 and 20 phr. The fiber length use in this study is 250 µm. The injection moulding technique was used to prepare the composite specimens for tensile, flexural and impact tests in accordance to the ASTM D5083, ASTM D790 and ASTM D256 respectively. The overall results showed that the composites reinforced with kenaf bast fibre had higher mechanical properties than kenaf core fibre composites. The results also showed that the optimum fibre content for achieving highest tensile properties for bast and core composites was 5 phr. It was also observed that the elongation at break for both composites decreased as the fibre content increased. However, a remarkable enhancement in the impact strength of the composites were observed upon the addition of 20 phr of bast and core fibre loading.

Study on thermal, mechanical and morphological properties of recycled poly(vinyl chloride)/fly ash composites

AbstractThe present study deals with the development of composite materials utilizing recycled poly(vinyl chloride) (r‐PVC) recovered from waste electrical and electronic materials and waste fly ash obtained from thermal power plants. The effect of the incorporation of fly ash on the mechanical, thermal and morphological properties of the r‐PVC matrix was studied. The primary characterization of r‐PVC and fly ash was done employing FTIR, EDX, particle size analysis and XRD analysis. Subsequently, fly ash with a particle size of approximately 9.29 μm was incorporated within the r‐PVC matrix. Composite sheets were prepared using a melt blending process followed by compression moulding. The mechanical test revealed an increase in the tensile strength and elongation at break of the r‐PVC/fly ash composite up to 30 wt% loading of fly ash beyond which there was a decrease in the tensile strength. The impact strength, however, decreased with increasing fly ash content in the r‐PVC matrix. The morphological properties of the composites showed a good distribution of the filler within the recycled matrix. The thermal properties of r‐PVC also improved with the incorporation of fly ash which was revealed from DSC and TGA studies. The water absorption test showed an increase in water uptake with the addition of fly ash in the r‐PVC matrix. © 2020 Society of Chemical Industry

Mechanical optimization of virgin and recycled poly(ethylene terephthalate) biocomposites with sustainable biocarbon through a factorial design

A statistical approach was taken to evaluate the effect of using recycled poly(ethylene terephthalate) (RPET), sustainable biocarbon and a chain extender on the performance of impact-modified PET biocomposites. Through a full factorial design, the extrusion-injection molded samples were tested for their tensile and impact properties. The mechanical results of the experiment were analyzed based on how the factors’ main effects and interactions between them varied the properties. The novelty is observed through the combination of the chain extender in the presence of the biocarbon reinforcing filler that enhanced stiffness and tensile strength through a synergistic interaction, while also providing a 278% increase in impact toughness over the biocarbon variant without chain extender. The inclusion of chain extender was the most important factor, with the biocarbon being the second most influential contributor, in causing changes in all mechanical properties measured, partially due to the morphological differences observed. Through this investigation, an optimized biocomposite formulation that had 28% sustainable content, with 10 ​wt% biocarbon, 25 ​wt% RPET substitution of PET and 1 phr of chain extender, was chosen that maintained a stiffness-toughness balance in the range of the statistical design.

Effect of recycled content and rPET quality on the properties of PET bottles, part I: Optical and mechanical properties

The effect of recycled content and type of recycled poly (ethylene terephthalate) (rPET) on the haziness; colour parameters L*, a*, and b*; total colour change; ultraviolet‐visual spectrum (UV‐VIS) absorption; and environmental stress cracking (ESC) of PET bottles was studied. Three series of PET bottles were made at a small scale production facility with same type of virgin PET and three different types of rPET with recycled contents of 25%, 50%, 75%, and 100%. Also, the particle contamination of the produced PET bottles was studied by dissolving bottle fragments and counting the insoluble particles. A linear relationship was found between the haziness of PET bottles and the particle contamination, with a coefficient of determination of 0.96. Linear relationships were also found between the colour parameters L* and b* and the particle contamination of the PET bottles, but the slope differed for each type of rPET. The origin of rPET (mono‐collection or cocollection) seems to be the crucial factor determining particle contamination and colour of the produced bottles. No correlation was found between the recycled content and the incidence of ESC. However, PET bottles in which high intrinsic viscosity (IV) values were measured showed lower chances of ESC than PET bottles with low IV values

Effect of recycled poly(vinyl chloride) on the mechanical, thermal and rheological characteristics of recycled poly(methyl methacrylate)

The recycled poly(vinyl chloride) (r-PVC) collected from the data cable has been incorporated into the recycled poly(methyl methacrylate) (r-PMMA) matrix in different weight percentage through the melt blending technique. The obtained recycled blends were analysed for mechanical, rheological, thermal and morphological characteristics. Among the various recycled blends formulated, 70:30 wt% of r-PVC/r-PMMA exhibits higher fracture toughness value. The rheological analysis highlights that recycled blends have pseudo-plastic characteristics. Furthermore, the storage and loss modulus values are decreasing with the increment of r-PVC in the recycled blend. The scanning electron microscope (SEM) study reveals the transformation of recycled blend matrix from brittle to the ductile character with the higher concentrations of r-PVC. Similarly, the water absorption, chemical resistance behaviour of the developed blends was depended on the concentration of r-PVC in the recycled blend.

Study of the Interaction Between Oligomerised Recycled Poly(ethylene terephtalate) and Concrete Waste

Aiming to assess the feasibility of a one-step processing, comprising simultaneously the mixing of polymer/filler and the modification of the particle surface, we prepared composites of recycled poly(ethylene terephtalate) and micronized concrete waste particles, using an oligomerising agent. The goal was to partially oligomerise the recycled polymer and foster the chemical modification of the concrete particles surface with these oligomers, to improve the dispersion and adhesion of the filler in the polymeric matrix. The composites were evaluated by thermogravimetry/derivative thermogravimetry, differential scanning calorimetry, Fourier transform infrared spectroscopy, wide angle X-ray diffractometry and rheological measurements. There was an improvement in the crystallizing effect of the filler in the composites with oligomerised polymer. We noticed a trend of reaction between the citric acid and the poly(ethylene terephtalate) oligomer in the Fourier transform infrared spectroscopy results. From the wide angle X-ray diffractometry analysis we assessed that the presence of the filler had more influence in the crystallinity of the recycled poly(ethylene terephtalate) than the degradation caused by the citric acid. The rheological measurements showed an increased cohesion of the internal structure of the materials in the oligomerised samples. We conclude that there is a pathway to obtain composites of recycled poly(ethylene terephtalate) and surface-modified concrete waste particles in a single step, by partially oligomerising the polymer in the molten processing.

Blend of recycled poly(ethylene terephthalate) and polycarbonate with polyaniline for antistatic packaging

Antistatic packagings are very important for proper transportation and storage of electronic components since these components can be damaged with electric overloads generated through rubbing. Therefore, the purpose of this study was to develop an innovative material for antistatic packaging with a sustainable character. For this, a blend of recycled poly(ethylene terephthalate) (PET), polycarbonate (PC), and polyaniline (PAni) was prepared by melt extrusion. Samples have a final content of 68 wt% of PET, 29 wt% of PC, and 3 wt% of PAni doped with cobalt (PAni-Co). The properties were determined by differential scanning calorimetry, thermogravimetric analysis, tensile testing, electrical resistivity analysis, and Fourier transform infrared spectroscopy. To the best of our knowledge, no previous work studied the incorporation of PAni-Co in PET/PC blend.

Recycled Poly(ethylene terephthalate) for High Temperature Solvent Resistant Membranes

Porous membranes of recycled poly(ethylene terephthalate) (PET) were prepared by nonsolvent-induced phase separation (NIPS) and evaluated for the first time for the filtration in high temperature solvents and other harsh environments. The PET was recycled from commercial water bottles. The morphology, pore size, and pore density were optimized by varying the composition of the polymer concentration in the casting solution, the solvent, and the nonsolvent bath in conditions of controlled humidity and temperature. Poly(ethylene glycol) (PEG) of 0.2 and 1 kg mol–1 was used as an additive and pore inducing agent. The filtration performance of the membranes was tested under different solvents and temperatures. The obtained PET membranes were successfully applied for ultrafiltration with a MWCO of 40 kg mol–1 in dimethylformamide (DMF) at temperatures up to 100 °C. PET membranes were found to be resistant to a wide variety of solvents as well as in chlorine and acid medium. They could be used as porous support for thin-film composite membranes and for different applications requiring high chemical and heat resistance.

Investigating the wicking behavior of micro/nanofibrous core‐sheath PET–PAN yarn modified by dimethyl 5‐sodium sulfoisophthalate

ABSTRACTThe present research aims at imparting an improved wicking ability to the recycled multifilament yarns by wrapping composite nanofibers to attain an efficient material for filtration purposes. Therefore, polyacrylonitrile nanofibers containing dimethyl 5‐sodium sulfoisophthalate nanoparticles were wrapped around the recycled poly(ethylene terephthalate) yarn by means of a novel electrospinning technique. Several tests were performed to investigate the parameters affecting wicking rise and moisture regain of the samples. Taguchi method was used in two separate designs (with or without nanoparticles). Some factors such as polymer solution concentration, mass ratio of nanoparticles, take‐up rate, and number of filaments were considered as the variable factors while yarn wicking rate and moisture regain were the response factors. It was found that the hydrophilic nature of nanoparticles together with the ultrafine structure of nanofibers provide yarns with enhanced wicking properties. Although solution concentration is the predominant factor in wicking rate of the yarns containing nanoparticles, the most effective factor in wicking rise and moisture regain for other cases is the number of filaments. The mechanism of nanoparticle effect on fluidic jet during electrospinning process is explained by theory of nanofluids stability which has never been validated experimentally in previous research studies. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48185.

Formation of high-density polyethylene–poly(ethylene-octene) core–shell particles in recycled poly(ethylene terephthalate) by reactive blending

Recycled poly(ethylene terephthalate) (R-PET)/high-density polyethylene (HDPE)/glycidyl methacrylate grafted poly(ethylene-octene) (mPOE) blends, in which the binary (HDPE/mPOE) dispersed phase was of a HDPE core-mPOE shell structure, were prepared. For this purpose, HDPE-g-mPOE graft copolymers were prepared in HDPE/mPOE blends via reactive extrusion with the presence of the free radical initiator dicumyl peroxide (DCP). Then, R-PET was blended with the HDPE/mPOE blends by melt extrusion. The effect of the DCP and mPOE content in the HDPE/mPOE blends on the phase morphology and mechanical properties of the R-PET/HDPE/mPOE blends were studied systematically. It was found that the blends containing reactive compatibilizer exhibited the encapsulation of the HDPE by the mPOE, forming core–shell particles dispersed phase morphology. The graft chains of HDPE-g-mPOE-g-PET formed by the in situ reaction between R-PET and mPOE phases reduced the interfacial tension. Consequently, the dispersed phase morphology was observed to form smaller diameter core–shell particles. The resultant blends exhibited an effect on both the thermal and mechanical properties. Differential scanning calorimetric analysis showed the dispersed phase particles could act as a nucleating agent in the R-PET matrix to improve the crystallization temperature, while the graft copolymers formed in the compatibilized R-PET/HDPE/mPOE blend decreased the nucleation activity. Notched Charpy impact strength and elongation at break of the R-PET were improved by forming the core–shell particles dispersed phase morphology.